The structure of aspirin is shown in table 20 of the data booklet. Suggest a suitable reagent for the conversion of aspirin to its sodium salt.

Explain the advantage of converting aspirin into its sodium salt.

Suggest a reagent that could be used to convert morphine into diamorphine.

Explain why diamorphine is a more potent drug than morphine.

\({\text{NaOH/N}}{{\text{a}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}{\text{/NaHC}}{{\text{O}}_{\text{3}}}\);

Do not accept alkali, base or \(O{H^ - }\).

Accept either a correct chemical formula or name.

increases aqueous/water solubility;

facilitates distribution (in the body) by the bloodstream / OWTTE;

ethanoic acid/\({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\) / ethanoyl chloride/\({\text{C}}{{\text{H}}_{\text{3}}}{\text{COCl}}\) / ethanoic anhydride/\({{\text{(C}}{{\text{H}}_{\text{3}}}{\text{CO)}}_{\text{2}}}{\text{O}}\);

Accept “acetic acid”, “acetyl chloride”, “acetic anhydride” or “ethanoyl-ethanoate”.

Do not accept “carboxylic acid”.

diamorphine is less polar/non-polar / morphine is more polar / polar groups in morphine are replaced with less polar/non-polar groups in diamorphine;

(less polar molecules) cross blood-brain barrier faster/more easily / (diamorphine) more soluble in non-polar environment of CNS/central nervous system / (diamorphine) more soluble in lipids;

Many candidates were able to give a correct reagent for the conversion of aspirin to its sodium salt. Incorrect answers included NaCl, Na and incorrect chemical formulas for sodium carbonate. In (a) (ii), the increase in aqueous solubility was necessary and increase in solubility alone did not suffice. This threw a number of candidates. The markscheme for (b) (i) was quite broad and most candidates scored one for the two similarities, though some did not understand that benzene is different to benzene ring and that -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{2}}}\) is not the phenyl group, which is actually -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\). As regards the difference, as previously hydroxide was not accepted for hydroxyl. Some candidates mixed up ethers with esters. In (c), many scored both marks though a few did not mention the non-polar nature of diamorphine.

Many candidates were able to give a correct reagent for the conversion of aspirin to its sodium salt. Incorrect answers included NaCl, Na and incorrect chemical formulas for sodium carbonate. In (a) (ii), the increase in aqueous solubility was necessary and increase in solubility alone did not suffice. This threw a number of candidates. The markscheme for (b) (i) was quite broad and most candidates scored one for the two similarities, though some did not understand that benzene is different to benzene ring and that -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{2}}}\) is not the phenyl group, which is actually -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\). As regards the difference, as previously hydroxide was not accepted for hydroxyl. Some candidates mixed up ethers with esters. In (c), many scored both marks though a few did not mention the non-polar nature of diamorphine.

Many candidates were able to give a correct reagent for the conversion of aspirin to its sodium salt. Incorrect answers included NaCl, Na and incorrect chemical formulas for sodium carbonate. In (a) (ii), the increase in aqueous solubility was necessary and increase in solubility alone did not suffice. This threw a number of candidates. The markscheme for (b) (i) was quite broad and most candidates scored one for the two similarities, though some did not understand that benzene is different to benzene ring and that -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{2}}}\) is not the phenyl group, which is actually -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\). As regards the difference, as previously hydroxide was not accepted for hydroxyl. Some candidates mixed up ethers with esters. In (c), many scored both marks though a few did not mention the non-polar nature of diamorphine.

Many candidates were able to give a correct reagent for the conversion of aspirin to its sodium salt. Incorrect answers included NaCl, Na and incorrect chemical formulas for sodium carbonate. In (a) (ii), the increase in aqueous solubility was necessary and increase in solubility alone did not suffice. This threw a number of candidates. The markscheme for (b) (i) was quite broad and most candidates scored one for the two similarities, though some did not understand that benzene is different to benzene ring and that -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{2}}}\) is not the phenyl group, which is actually -\({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}\). As regards the difference, as previously hydroxide was not accepted for hydroxyl. Some candidates mixed up ethers with esters. In (c), many scored both marks though a few did not mention the non-polar nature of diamorphine.